<html>
<head>
	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
	<title>Document</title>
</head>
<body>
	<p>如果时间早于 20:00，会获得问候 "Good day"。</p>
	<button onclick="myFunction()">点击这里</button>
	<p id="demo"></p>
	<script type="text/javascript">
		function myFunction(){
			var x="";
			var time=new Date().getHours();
			if(time<10){
				x="Good morning";
			}
			else if(time<20){
                x="Good day";
			}
			else{
				x="Good evening";
			}
			document.getElementById('demo').innerHTML=x;
		}
	</script>
</body>
</html>